Trigger system for gun turrets



Aug. 20, 1946. G. w. PONTIUS, 30.. ET AL 2,406,102

TRIGGER SYSTEM FOR GUN TURRETS Filed April 20, 1942 6 Sheets-Sheet l MVEIVTOIPS' ATTORNEY Aug. 20, 1946. s. w. PONTIUS, V3D., ETAL 0 TRIGGER SYSTEM FOR GUN TURRETS Filed April 20, 1942 6 sh ets-Sheet 2 g G. w. PONTIUS, 30., ET AL ZAGSJZQZ TRIGGER SYSTEM FOR GUN TURRETS Filed April 20, 1942 6 Sheets-Sheet 3 Aug. 2, m a. w; PONTEUS, 30., ET AL 9 TRIGGER SYSTEM FOR GUN TURRETS Filed April 20, 1942 e Shee s-Sheet 4 Filed April 20, 1,942 6 eets-Sheet 5 GEORGE wpomflas ARTHUR H w/waw BY FAANA v. KUZM/T Aug. 29, 14. G. w. PoN'nus, an, ETAL 2,406,12

TRIGGER SYSTEM FOR GUN TURRETS Filed April 20, 1942 6 sheets-SheetG Patented Aug. 20, 1946 TRIGGER SYSTEM FOR GUN TURRETS George W. Pontius, III, Arthur P. Wilson, and Frank V. Kuzmitz, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application April 20, 1942, Serial No. 439,622

2 Claims.

This invention relates to gun turrets and more particularly to an electrical system for firing the guns of a turret mounted on an airplane.

The firing of airplane guns must be rapidly performed since the sights are on the targets for fraction of a second only. This necessitates power control of the trigger mechanism, since the slightest amount of resistance to manual effort will slow up the firing. A simple push button electrical switch is therefore used, and to decrease the size of this switch, it is connected to operate a relay which in turn applies the electrical current to the power devices for firing the guns.

In turrets mounted in airplanes, means must be provided to keep the guns from shooting at parts of the airplane and thus injuring it. This cut-out means must be automatic and must not interfere with the movement of the turret.

The invention will be described as applied to turrets for the bottom and upper surfaces of airplanes respectively. The lower turret i shown in more detail in application Serial No. 391,911, filed May 5, 1941, on behalf of Pontius.

It is an object of the invention to provide power means for firing the guns of a turret.

It is a further object to provide automatic cutout means for the firing control of a gun.

Other objects and advantages of the invention will be apparent in the following description and claims.

In the drawings forming a part of this specification,

Figure 1 is substantially a side view of an airplane having a lower turret with a trigger system made in accordance with the invention;

Figure 2 is an enlarged sectionalview of the airplane of Figure 1 in the region of the turrets, showing the turret in an operative position and being at the instant controlled and fired by a gunner;

Figure 3 is an isometric partly schematic view of the turret in an extended position, parts thereof being in isometric section to show the mechanical parts and movements;

Figure 4 is a phantom view of the lower turret which is shown in broken line with the electric trigger circuit superimposed thereon;

Figure 5 is a wiring diagram of the trigger circuit of Figure 4;

Figure 6 is a perspective view of an airplane having an upper turret with a trigger system made in accordance with the invention;

Figure 7 is a vertical section through the airplane and the canopy of the turret shown in Figme 6 showing a gunner operating the upper turret with the guns pointed toward the rear of the airplane;

Figure 8 is a schematic isometric projection of the mechanical parts and movements of the upper turret; and

Figure 9 i a phantom View of the upper turret which is shown in broken lines with the electric trigger circuit superimposed thereon.

The placement of the lower turret in an airplane is shown in Figure 1. Airplane I00 retain a turret I02 in a retracted position in the bottom of the fuselage. When thus retracted the bottom of the turret is substantially flush with the surface of the fuselage, giving no substantial interference to the slipstream.

The turret I02 is shown on an enlarged scale in an extended position in Figure 2. A gunner I04 kneels on a cushion I06, his chest supported on a rest I08 attached to the turret. The gunner looks through a periscope in the turret to sight the guns I I0, and with his right hand operates the electrical power controls for the movements of the turret and the gun, while with his left hand he operates a trigger control. Guns wells II2 are provided in the airplane I00 at the rear of the turret as a housing for the guns when the turret is retracted, at which times the guns IIO will be horizontal.

The mechanical parts relating to the movement of the turret are shown in diagrammatic form in Figure 3 wherein the turret is shown in an extended position. The turret I02 is supported on a four-armed spider II 4 which is ecured to structural members such as N5 of the airplane I00, and which has a central collar II6. Ball bearings such as II 8 rotatably support an internally threaded sleeve I20 within collar IIB, which sleeve has an upper ring gear portion I22. A threaded column I24 i threaded into sleeve I20 and is thereby supported within spider IN. A head unit I26 rotatably ride on the upper end of column I24 and is itself restrained from rotation by a telescoping yoke member I 28 secured to the outer end of one arm of spider II 4.

A single power source is used to rotate the sleeve I20 in order to rotate the turret in azimuth or optionally to retract and extend the turret. Thi power source is an electric motor I30 suitably secured to the spider H4. The motor I30 drives a motor shaft I34 to which i secured a worm I36. Worm I 36 engages a worm wheel I 38 which is secured to a drive shaft I40 having suitable bearings which will be later described. A worm I42 on shaft I40 engages ring gear I22, causing the sleeve I26 to rotate within spider collar H6. Through the gear train thus described, electric motor I38 i made to rotate sleeve I26. The motor I30 can be reversed by reversing its field current, thus reversing the direction of rotation of sleeve I26; The gear train provides a large reduction in rotation allowing the use of a very high speed motor, to provide a high power to weight ratio.

Also shown in Figure 3 is a shaft I l-9 driven by motor worm wheel I38 and having a worm Il on the outer I5I is similar to that of drivingworm M2 at the column resulting in compensator shaft 662 making a complete rotation for every rotation of column I24. In other words, the azimuth trigger cam AEEBi synchronized with the azimuth movement of the turret.

The column I24, and thereby thetur ret also. may be rotated in azimuthorretracted and/or extended, by selectively connecting column I2 1 with sleeve I28 or with non-rotatablehead I25; This selective connection is performed by an L- shaped key I'M. held.in a hole' through column I24 and selectively engaging an internal notch I58 insleeve I26, .or an external notch I52 in non-rotatable. head I26.v The mechanism .for moving key I44 hasbeen described inPontius application Serial No. 391,911, and has been described fully and claimed in Pontius et al. application Serial .No. 407,468, filed August 19, 1941,

now Patent No. 2,389,997, dated November 27,

When key I44 engagesnotch I52 in non-rotatable head I26, column I24 is restrained from rotation. If motor I30. now rotates ring gear I22, and thereby sleeve I26, thefcolumn I24 will be raised or lowered according to the direction of rotation of sleeve I22. The head I26'is lowered or-r-aised with column I24, and .the yoke member I28 will telescope and extend and will" act atiall times to keep head I26 from rotating. InHthis waytheextension and retraction of turret IE2 is accomplished. ,When the turret I62 is extended the key 34 may be moved to engage notch 1553 in sleeve I26 and the column I24 will as sleeve I29 rotates, and thus, provide the operativemovement of rotationin azimuth. It will be noted that in such case the key IMIwill be out of notch I52 and there is no restriction on end thereof. Worm I5ldrives a worm wheel 6% which in turn drives a com pensator shaft 662 havinga rotarytrigger earn 408 secured thereto. The gear reduction at worm} rotate the movement in azimuth. The column, I24 can be rotated continuously in either direction, for any given number of rotations.

Certain parts of the turret are fastened onthe lower end; of column I2t.. These parts include a rotatable shaft secured. A worm wheel sector I is secured to haft I56 and is engaged by a worm I82 fastened to a drive shaft. I6 3. 'Drive' shaft I64 in turn is driven by a worm wheel I66 secured thereto, which is drivenbya worm [68 secured to .a motor shaft- I'Ii] of an electric elevation motor Alsoshown in Figure 3 is a gearing system for an elevation trigger cam. Connected to motor worm wheel I66 is a shaft I'II having a worm IIIatsecured to one end thereof. Worm Illa drives a compensator worm wheel 6I2 which in turn drives an elevation compensator shaft 6M. Fastened to the end of shaft GM is an'elevation trigger cam. 416. The gearreduction at worm I'I'Ia is not the same as at worm wheel sector I56 to which the guns I-III are 4 I60 and shaft 6l2 rotates approximately three times faster than gun shaft I56. This is permissible since the greatest movement of the guns in elevation (or zenith) is about 95, and the increased movement of shaft 6I2 gives greater sensitivity. d

The elevating: gear train and its actuating motor are adapted to elevate or depress the guns, depending upon the direction of rotation of motor I72, which is reversed by reversing its field. Theguns II'Ilcan be elevated above horizontal as far as is permitted by the shape of the airplane in which the turret is mounted, and can be depressed 'to' point straight down. The elevation: (or zenith): are as will be described for purposes of illustration, will be limited to a are from horizontal to straight down.

The trigger circuit for the turret is shown in Figure 4 as applied to the turret and is shown in diagrammatic form in inset Figure 5.. Provision must be made for a cut-out mechanism to prevent the guns from shooting at various parts of the airplane. When the guns are horizontal andpointing forward they might shoot into the revolving propellers and they might shoot into the fuselage directly in front ofithe turret. 7 Also, when the turret is designed to shoot'above horizontal at the rear, the guns might shoot at the tail wheel. Thus the circuits and mechanism which will now be described provide cut-out means for the trigger fire at these danger points.

As explained above, the trigger cut-out is necessary only when the guns are elevated'to' a substantially horizontal position, and then only for certain forward positions. The azimuth trigger cam 408 has been previously referred to in connection with Figure 3 and is shown in Figure 4 near the upper. part of the figure. As shown in Figure 4 the cam 468'is notched for those'forward positions in which the gun should notshoot. The elevation trigger cam'i llll .has been previously referred to in connection with Figure 3 and is shown in Figure 4 near the lower right corner of that figure. As shown in Figure-4 the elevation cam Mn is notched for the horizontal position at which the guns should not shoot. As explained with reference to Figure 3 the azimuth cam 468 and the elevation cam 4H] are geared to move in synchronism with the azimuth and elevation movements of the turret respectively;

Referring to Figure 5, currentfrom battery BI flows through wires 2, 8 and 32t'o an armature S1 of a relay L'I, which when energized passes current through wires 33 and 34 to two identical firing solenoids FS one for each gun H0. 'The relay L1 is energized by current flowing through a wire 35 which current is regulated by three switches, a firing switchSl I-, an azimuth switch SI3 and an elevation switch SM. Branchingfrom a wire 8 is a wire 36 which leads to azimuth switch SI3, which is normally closed by cam 468 and is opened only. when one of the. notches in the cam 4B8 come opposite the switch. The other end of switch SI3 is connected to a wire 31. which leads to a wire 38 which leadsto'fi-ring switch SII referred to above.

Branch wire 26 leads from wire a to elevation switch SM which is normally closed by elevation cam 4H), and is opened only when the notch in the cam is opposite the switch. A wire 39 is connected to the other sideof elevation switch SM and leads to wire 38 also. Wire 38 is connected as stated above to firing switch SII the other side of which-is connected to relay wire 35.

From the above description of Figure 5, it is apparent that the guns can be fired through firing solenoids FS at nearly all times. If the guns areelevated to a horizontal position the switch S14 will be broken but current might nevertheless flow through switch Sl3 to trigger switch Sll. When azimuth switch SL3 is open current might likewise flow through elevation switch Sl4. It is onlywhen both switch Sl3 and switch Sl4 are open that the guns cannot be fired. The switches Sl3 and SM will both be opened only when the guns are pointed at some part of the ship corresponding to the combination of notches on azimuth cam 508 and elevation cam 4| 0.

This trigger circuit will now be applied to Figure 4, and the corresponding circuit can be traced also on Figure 5. Current is derived from battery Bi and'fiowsthrough wire l,"through relay Ll (which is energized by closing a shunt circuit through a wire II], a switch SI in a controlhandle 504, and the Winding of the relay LI), and through wire 2 to wire 8. The branch 32;from wire 8 leads to the firing relay L1 and suppliescurrent for firing the guns when relay L1 is energized. Another branch from wire 8,

wire 26, leads to theelevation compensator box which retains cam 4 i 0, and is connected to switch S14. The wire 39 leads from the other side of switch S44 back up the central column to join wire 31 at its junction with wire 38.

The other branch of the parallel circuit to wire 38 is shown at the top of Figure 4. Wire 35 branches from wire 8 to lead to switch SE3 which is connected by wire 31 to wire 38. Firing switch SI l is placed in a trigger grip 404 and is actuated by trigger button 405 which the gunner presses with his left thumb. A wire 40 leads from firing switch SH to a. safety switch SI2, the other end of which is connected to the relay wire 35 leading torelay L1. The switch S14 and wires 8, 26 and 39 of the elevation cam circuit form a parallel circuit with respect to the switch SH! and wires 8, 36, and 31 of the azimuth cam circuit. The parallel circuit formed by the azimuth and elevation circuits is in series with the firing switch SH and the relay L1.

' The operation of the trigger circuit for the lower turret as shown in Figure 4, and traceable on Figure 5, is as follows. Safety switch SIZ is usually open, at which times the guns cannot be fired. After the turret is extended and ready for combat, the gunner will manually close safety switch Sl2. Th gunner will now be gripping the control handle 504 with his right hand, closing switch SI to energize relay LI and pass current to the electrical system of the turret shown in Figure 4. When the gunner desires to fire the guns, he places his left hand on the trigger grip 404 and presses button 405 closing switch SH. Current will usually flow from either wire 31 or 39 through wire 38 and switch SH through wire 40 and safety switch S|2 and through wire 35, down the central column to relay L7. When relay .L1 is energized current flows to the firing solenoids BS in housings 406 and these in turn cause the guns I H] to fire.

' If the guns are pointing forward at an angle in line with the lower parts of the airplane, the azimuth cam 408 will rotate in synchronism and one of its notches will allow switch Sl3 to open. Current can nevertheless flow to firing switch SI I from wire 39 and the guns can still be fired. If the guns should now be elevated to a position in line with the lower parts of the airplane, the elevation cam 4|0 would rotate in synchronism and its notch wouldallow switch S|4 to open.

With both switch Sl3 and switch SM open no current will flow to firing switch SI I and the guns cannot be fired. Thus through the means of the two dimensions of elevation and azimuth, danger areas can be definitely plotted, and through the use of cams synchronized with movement in azimuth and elevation, cut-out means for the trigger circuit can be provided for these danger areas.

The mounting of the upper turret is illustrated in Figure 6. An airplane 200 has mounted on the rear part of the fuselage a turret 202. The turret is adapted to rotate 360 for a given number of rotations.

The mounting of the upper turret is shown in detail in Figure 7. 7 Secured to longitudinal members 204 of the airplane 200, is a base member 206 which rotatably supports a column 208. Secured to the top of rotatable column 208 is a frame member 2| 0 to which the guns 212 are mounted for rotation in elevation. Also secured to frame 2| 0 is a periscope 300 and an ammunition can 2I6. A transparent canopy 2|8 covers the top of the turret and is secured to frame 2 l0.

The turret is operated by a gunner 220 sitting on a seat 222 secured to the column 208 and placing hi feet on a rest 224 also secured to the column 208. With his right hand the gunner 220 grips a control handle 402 which he manipulates to rotate the turret in azimuth in either direction or elevate or depress the guns. The gunner sights the guns by looking through periscope 300, moving the turret and guns in alignment with the target. All the mechanism mounted on the column 208 rotates in azimuth, and the guns 2l2 and the movable part of the periscope rotate in elevation as well as azimuth.

The mechanical parts and movements of the turret are shown schematically in Figure 8. At the bottom of the figure a high speed electrical motor 228 drives a motor shaft 230 to which is secured a worm 232. Worm 232 drives a worm wheel 234 secured to a drive shaft 236 to which i secured at the other end a driving worm 238. Drive worm 238 engages a worm wheel 240 secured to rotatable column 208, and drives colum 208 in rotation in either direction depending upon the direction of rotation of azimuth motor 228.

Also secured to worm wheel 234, is a compensator drive shaft 242 to which is secured a compensator worm 243. Worm 243 drives compensator worm wheel 246 to which is connected Compensator shaft 248. Mounted on compensator shaft 248 i a trigger cam 508. The gear reduction between compensator worm wheel 24B and worm 243 is the same as that between column worm wheel 240 and driving worm 23B, resulting in compensator shaft 248 rotating one revolution for every revolution of column 208 and rotating in synchronism.

Rotatable column 208 is preferably made of aluminum or .magnesium to reduce weight. The frame 2l0 secured to the top of column is also preferably magnesium or aluminum and may be made by casting. An opening 2 in the frame 2) provides a place in which the gunner may place his body for operating the turret. The guns 2 I2 are secured to a rotatable gun shaft 244 supported near each gun by frame brackets 2l3.

Gun shaft 244 is driven in elevation by a. high speed electrical motor 241 positioned within a well 209 in frame 2l0. Motor 241 drives a motor shaft 248 to which is secured worm 250 engaging driving worm wheel 252 mounted on a drive shaft 254. Secured on the other end of drive shaft 254 7 is drivingworm 256 engaging l a worm" wheel sector'258 -secured to-gun shaft 244. The gun shaft is rotatecl in either direction by reversing elevation motor 247-, elevating or depressing the guns according to direction of rotation of motor 241.-

The elevation compensator drive is alsoshown in'Figure 8 and is obtained through: abevel gear 262 secured to shaft 244, and driving a matching bevelgear 264 which drives elevation compensator shaft 266. l 'astened to compensator shaft I66 is an elevation trigger Cam Since the elevation movement of the gun's'is about 90, the rotation of compensator shaft 2651s multiplied about three times to increase sensitivity of the cam control.

The trigger circuit and charging circuit for the guns of the upper turret areshown' in Figure 9 and it will be noted. that the circuit is similar to that of the lower turret. Parts of the turret already identified are shown in broken outline including the center post 2ll8, the ring gear 245, the-driving worm 238 andthe azimuth motor 228.

Als shown is the-azimuth compensator drive including Worm wheel 245and the driven azimuth trigger cam 503. On the upper end of the turret the guns 2 i2 are mounted on shaft 244 and driven in elevation by elevation. motor 241. Also shown in dotted outline is the elevation compensator drive including shaft 266: on which is mounted elevation trigger-cam 5| 0.-

Theelectrical trigger circuit and electrical and hydraulic charging circuit is superimposed in solid lines on'the dotted outline of the turret. A battery'BZ supplies Current to a'wire 5| leading through'the brush box, up the column, and to the control handle 462' where it connects to a switch S21. Switch- S21 is the main power switch for passing all current to the turret and when the gunner grips-control handle 45?. he closes switch S2! by the act of grasping the control handle. Because of this type of grip control the power will automatically be cutoff if the gunner is shot thus preventing injury to the turret or the airplane in which it is mounted.

ReferringtoFigure 9 when switch S2 I is closed current flows to a wire 52";vi'rhich is connected to both'fingers of a double relay L2. Energizing rela L2 causes current to flow through Wires 54 and 53-to firing solenoids=F3 and F4 in housings 5l2 secured to the guns, causing the guns 2|2 to fire.

Branching fromwire'52 near the center'post is a wire 55 leading'to a switch S22-the other end of which is connected to awire 56' leading down the column 268 and ou't' the brush box to a sole noid H of an hydraulic valve 590'. Switch S22 is manually' operated by the gunner whenever eithergu'n 2I2 jams; Closing switch S22 passes current to valve 59li"causing it to open to pass hydraulic fluid from aninlet'pipe- 592 to a gland conduit 584 through an hydraulicgland 580' to a conduit 586. A- fitting 594' isconnected to a conduit 585which passes fiuid thereto, at which point flexible tubing 59'! is connected leading to chargers 5H5. After the charging is completed switch'S22 is opened'deenergizing valve 555 and allowing it to return to" normal at which time the hydraulic fluid in the charger will flow through the valveto exhaustconduit 596.

Still referring to Figure9, in certain positions of the turret, the guns 2l2 will be pointing at a part of the airplane and if firing: were'possible, injury to the airplan'e'iwould' result. For this purpose a cutout mechanism for the'trigger sys-' tin'is provided, which 'will now be" described;

Also branching from wire-52 is :a. wire 51 leadingto'two wires 58 and 59;. Wire" SB-Jleads to a switch S23 actuated byele'vation cam.5l.0.- Cam 5l01is notched in. a portion; corresponding to the elevation: position of "the guns at: which they would fire upon thexairplane.- When'the guns move in elevation to this position then'otch'open's switchS23 and no current can pass at thatpoint to supplyatrigger-switc-h,

The other branch wire59 connectedto wire 5'!" leads down the columnand throughlthe brush box to d, switch S24 actuated: by azimuthtrigger cam 508. Cam 508 is notched ina portion-or portions corresponding to theazimuth position of the turret at which the guns would fire-upon the airplane. When cam 508 rotates so that-the notched. portion is opposite the switch S24 =no current will fiow tothe trigger switch at that point. 7

Connected to switch S24 is a: wire 53 leading through the brush box up the centrar'column; to-join a wire 6| leading from switch S23. Wires Giland 6| are connected'to a wire-62 leading to a trigger switch S25 in the control handle 402.- When the gunner desires tolfire he closes trigger switch S25 with his finger, passing current the wire 63 leading to relay L2. If current passes through wire 63 the relay will be energized'clos ing the circuit to the firing" solen'oid'sF3 and F4 causing the guns to' fire} In operating the charger circuit of Figure 9, the gunnerwill be seatedin the turret gripping control handle 402 shown in Figure 7. Gripping control handle 40-2 closes p'owerswitclr S2l permitting current to fiowiromjbatte'ry B2up wire 5! to the switch S2I and through wire 52. Branch wire 55 is now hot, and if the guns should now jam, or if for other reasons the gunner should desire to c harge' the guns, he merely closes charger switch S22 with his left hand while gripping handle 402 in his right hand.v Current then. passes through wire 56 down column 208 to .the solenoid valve 590. Valve 590opensto permit hydraulic fluid under pressure to" enter conduit 554, pass throughgland 580,111) column conduit 586 and out voffitting 594 to the hydraulic chargers 5 I 4, The chargers then retract the bolt of guns 2l2' charging them; 7

After the charging is completed the gunner rejleases switch S22"Whi ch' opens, deenergizing'qth'e solenoid H of valvef590. The valvethen returns to normal connecting tube 584 with theexhaust line 596; A quantityof. liquid will then flow out of the chargers and connected conduits s'uflicient to. allow the chargers to return to'their starting position.

' In operating. the upper turret trigger system shown in Figure 9 the gunner grasps control handle 402 andiin do'i'ng so closes-powerswitch S21. This permits now of current through wire 52 to wire 5'! .from there to the wires 58 and 59 forming part of a parallel" circuit to fir'ing' switch S25. Current in wiress'm'ay be interrupted by a switch S23 actuated byigcam 5H1 synchronized with the elevation movement of the guns 2 l2. The otherlbranch'of the'parall'el circuit, wire 59 leads down the'column andcurrent flow isint'errupt'ed by switch S24actuated by cam sas syric'hronized with the azimuth .movements of the turret. vVlfheni elther'carh' 5H1 ortua rotates to a point corresponding" to'thepoint at which bullots would hit the airplanejthe respective circuit is broken. When" the azimuth and elevation positions both correspondto a position where the bullets will strike part o the airplane, no

current will flow through either branch of the parallel circuit and closing the trigger switch S25 will have no effect.

When the position of the turret and guns is other than the cut-out position, current will flow through one or both branches of the parallel circuit wires 58, BI, 59 and 60 respectively to wire 52 passing current to firing switch S25. When the gunner desires to fire he merely presses switch S25 with his finger, passing current through wire 53 to relay L2 and actuating it. Current then flows from wire 52 to wires 53 and 54 to the firing solenoids F3 and F4 causing the guns to fire. Release of switch S25 breaks the circuit to relay L2, the power circuit to the firing solenoid is broken and the guns cease to fire. A relay control of firing is used to reduce the size of the manual switch to a minimum and increasing ease of operation.

Although this invention has been described with reference to particular embodiments thereof, it is not limited to these embodiments or otherwise except by the terms of the following claims.

What is claimed is:

1. In combination, a turret movable in azimuth, guns mounted on said turret for movement therewith in azimuth and relative thereto in elevation, an electrical system comprising a source of current, a firing circuit includin a firing device for each gun, a first circuit normally open and including a manually operated switch for closing the aforesaid first circuit, means controlling the firing circuit and including a relay coil in the first circuit, said means being responsive to closing the first circuit to thereby close the firing circuit, a cam constructed and arranged to follow the guns in azimuth, said cam having notches therein corresponding to positions of the guns in azimuth where it is desirable to disconnect said devices, a first means in said first circuit arranged to cooperate with the notched portions of the cam for opening the first circuit, a second cam constructed and arranged to follow the movement of the guns in elevation, said second cam havin notches therein corresponding to positions of the guns in elevation where it is desirable to disconnect said devices, a second circuit normally open and including said relay coil and said manually operated switch for closing said circuit, and a second means in the second circuit connected in parallel with said first means, said second mean arranged to cooperate with the notched portions of said second cam for opening the second circuit, whereby the firing devices are disconnected from the firing circuit only if said first and second means are cooperating with the notched portions of said first-named cam and said second cam respectively.

2. In combination, a turret movable in azimuth, guns mounted on said turret for movement therewith in azimuth and relative thereto in elevation, an electrical system comprising a source of current, a firing circuit including a firing solenoid for each gun, a series parallel circuit including a manually controlled switch arranged in the series portion of said last-named circuit, a normally open switch in the firing circuit, a relay coil in the series portion of the series parallel circuit and constructed and arranged to close said normally open switch in response to energization of the relay coil when the manually controlled switch is closed, a pair of cams one of which is constructed and arranged to follow the move ment of the guns in azimuth and the other of which is constructed and arranged to follow the movement of the guns in elevation, said cam which follows the movement of the guns in azimuth having notches therein corresponding to positions of the guns in azimuth where it is desirable to disconnect said solenoids, said cam which follows the movement of the gun in elevation having notche therein corresponding to positions of the guns in elevation where it is desirable to disconnect said solenoids, and means in the parallel branches of said series parallel circuit which concurrently cooperate with the notched portions of said azimuth and elevation cams at times for causing deenergization of said relay coil to permit the normally open switch to open to disconnect said solenoids, said means being constituted to cause energization of said relay coil when the means of either parallel branch ceases to cooperate with the notched portions of its corresponding cam.

GEORGE W. PONTIUS, III. ARTHUR P. WILSON. FRANK V. KUZMITZ. 

